Van der Giessen-de Noord Blasting and Painting Halls
15 years ago Dordrecht-based Straaltechniek International BV started with the specialization in blasting and spray painting systems. Through the years the continuing development in in-house engineering has led to the ability to design and manufacture equipment on its own. Sales of these systems to abroad is through four parent companies, viz. two in Germany, one in Belgium and one in Norway. In April 1995 the company was awarded with an order from Van der Giessen-de Noord Shipbuilding Division for the delivery and installation of two fully equipped blasting and spray painting halls, both completely fitted with highly advanced equipment.
Environmental Criteria
Each of the two blasting and spray painting halls have an overall dimension of 32.5 x 20.5 x 15.5m. The so-called technical space has a dimension of 33 x 7.2 x 15.5m and features three floors.
The principal's starting point of view for the construction of the two new halls was to obtain an optimum preserving quality for their vessels in compliance with nowadays rules with regard to environmental protection and the Nuisance Act. Furthermore, the design of the new facilities is such that a fast throughput time can be realised, thus coping with the need for more efficient preserving and enabling the shipbuilder to run in connection with the production speed of ships.
For this reason in both halls blasting, spraying and drying can be carried out simultaneously; a so-called combined hall. According to this setup work can be carried out, for instance, with blasting work in Hall No. I, while spraying or drying work is carried out in Hall No. II or reverse. It is also possible that in both halls spray painting, drying or a combination is carried out simultaneously. Al these options are controlled and safeguarded by a highly advanced control system.
Technical Features
As mentioned, the complete technical equipment is distributed over three floors. These include:
- two dust collectors (total capacity of 110,000m3/h);
- six paint spray booths
The design of the new facilities is such that a fast throughput time can be easily realised
(total capacity of 210,000m3/h);
- two heating units (total air capacity of 110,000m3/h).
For an environmental-technically reason blasting is carried out with 'cast iron grid' as blasting medium which can easily be recycled. In order to reclaim and clean this cast iron grid use is made of only one conveying and transport system for both halls, featuring transport screws, an elevator and a blast medium cleaner, which returns the cleaned blast medium back into a 60 tons silo where eight blastpots are installed. Grid blasting can be carried out simultaneously with a maximum number of eight persons. The dust collectors have a capacity to ensure a perfect sight during blasting. The paint spray booth exhaust system has been such designed that painters can work in a safe and climatologi-cal accepted area. The heating installation is in capacity to heat up both halls simultaneously up to 15 degrees during spray painting, even at an outdoor temperature lower then minus 10 decrees Celsius.
The two 45kW dust collectors, each with a capacity of 54,000m3/h, are fitted with exchangeable Big Bags and can handle dust emissions up to 2mgr/Nm3. The six paint spray booths - three per hall - each have a capacity of 35,000m3/h. Each hall furthermore has one mixed air heater with a nominal output of 569kW and an air capacity of 55,000m3/h. Compressed air is derived from three 21 m3/h air compressors, each fitted with an air dryer, a pressure vessel and a piping network system. In order to save energy there has been opted for heat generation from the compressors through an electro-pneumatic air duct system. This system has also been implemented on the ventilators of the dust removal systems. The technical installation is fitted with three storage containers, two for storing paint etc. and one fully equipped with paint pumps. The complete electrical equipment is controlled through a central switchboard. Each hall is furthermore fitted with thirty-two 400W industrial lighting fixtures.
All walls are cladded with wall protection, consisting of three metres high black rubber with steel and above that non-flammable sail cloth. The concrete floors have been fitted with 12mm thick steel plates.
Separation Method
After the iron grid has disappeared in the gratings in the floor it is via dosing plates transported to an elevator by means of a conveying screw. The elevator has a capacity of 60t/h and features a conveying belt with a band width of 180mm. The elevator belt is fitted with heavy steel plate buckets and can be adjusted in length. The drive rolls of the belt are fitted with a special synthetic sealing, which is fully resistant against the agressive impact of the grid medium. A silo blast medium cleaning combination has directly been fitted under the outlet of the elevator through a fixed joint. Between the silo and the elevator outlet a 650mm wide blast medium cleaner has been fitted, comprising of two parts, viz. a mechanical sieving machine driven by a vibrating motor and a so-called cascade cleaner or air separator. This 650mm wide cleaning unit is the most advanced and effective grid cleaning unit currently available. All coarse-grained contaminants are led through the vibrating mechanical sieve which is executed with a 5mm mesh perforation and separated from the blast medium flow and subsequently discharged through a chute to exchangeable plastic bags. What is left of the blast medium is led to the air separator and is exhausted through a separate exhaust Pat-Jet filter.
The air flow separates the lighter contaminants out of the blast medium flow. By accurate adjustment of the air separator both heavy and light-weight particles are separated from the flow. The heavy components are led to a plastic bag and the light-weight dust components with the air flow to the cartridge filter where further separation takes place. The suction is for this reason fitted with an adjustment valve.
Summary
By an in-depth preliminary study of Van der Giessen-de Noord Shipbuilding Division on the location of the halls and the throughput times Straaltechniek International BV has succeeded in building two preserving halls wherein the applicator, De Koning Straal- en Schilderwerken BV, can carry out preserving jobs under safe and good climatological working conditions guaranteeing a constant quality. By meeting in advance the new standards Van der Giessen-de Noord is making sure that it has found the competitive edge to stay ahead in a still increasing and highly competitive market.